The admission by Nobel prize-winning novelist Guenter Grass that he served in the notorious Waffen SS during World War II has sent shockwaves through Germany and neighbouring Poland.

The Waffen SS was the combat arm of Hitler's dreaded SS paramilitary force, which was responsible for atrocities throughout Nazi-occupied Europe.

Guenter Grass was born in the northern port city of Danzig - now Polish Gdansk - in 1927.

His father was German, his mother Kashubian - a member of a small Baltic community which, depending on your point of view, speaks a peculiar Polish dialect or a distinct Slav language.

Moral authority

Much of Grass's writing - starting with The Tin Drum in 1956 - is located in and around his home city, with its complex and ultimately tragic history of mixed languages, cultures and divided political loyalties.

Grass also presented himself as a moral authority for post-war Germans.

Politically on the left, he attacked what he saw as his country's often superficial reckoning with the Nazi era.

When the Berlin Wall came down in 1989, he advocated the maintenance of two separate German states, arguing that a reunited Germany would eventually resume its old nationalistic bullying ways.

For his German critics, the shock is not so much that he was in the Waffen SS - by the time he joined in 1944 most members were young conscripts rather than committed Nazi zealots - but that he took so long to own up.

It has been pointed out that if his SS membership had been known at the time, he would probably not have received the Nobel prize for literature - even though, on merit, he deserved it.

It has even been suggested that his "revelation" might have been a publicity stunt, ahead of next month's publication his autobiography, called Peeling Onions.

Polish unease

In Poland, Gdansk city council is expected to discuss withdrawing his honourary Gdansk citizenship later this month - though a spokesperson is reported as saying a majority of councillors appeared to oppose the idea.

Eastern Europe still bears many scars from the Nazi terror

However, Lech Walesa - Poland's former president and former leader of the Solidarity movement - said from from his Gdansk home that he thought Grass should surrender his citizenship voluntarily.

The Czech PEN club is also considering whether to withdraw the prestigious Karel Capek Prize, awarded to Grass in 1994.

It turns out that Guenter Grass was a trooper in the SS Frundsberg Division, which fought against the Allies in Normandy and at Arnhem, and later against the Soviet army in Pomerania and Saxony.

Grass himself claims he never fired any shots and was a poor soldier.

It has to be said, that up to now, the Frunsberg Division has not been implicated in any major atrocities or war crimes - even though the SS as a whole was classified as a criminal organisation after the war.

Grass's own lack of candour about his past can be seen as an ironic commentary on his own insistence that Germans need to make an honest appraisal of their own horrible past.

For many, his status as a moral authority will have been compromised for good.

The latest revelations also come at a sensitive time in Germany's relations with its eastern neighbours, especially with Poland, run since last year by a centre-right government not afraid to make political capital at home by appealing to residual anti-German sentiment.

Opinion polls suggest that most Poles now see the Russians as the main potential threat to their country.

But renewed German interest in the fate of the expelled inhabitants of the former Polish-German borderlands - an interest that Grass himself has stimulated through his recent writing - has revived public unease in a Poland now supposedly Germany's friend and ally in the European Union and Nato.